We want to say that the operating system is very necessary and useful thing in ours computers. Without the operating system, your computer is piece of irony. An operating system (OS) is a set of computer programs that manage the hardware and software resources of a computer. An operating system processes raw system and user input and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. At the foundation of all system software, an operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking and managing file systems. Most operating systems come with an application that provides an interface to the OS managed resources. These applications have been command line interpreter as a basic user interface, but more recently have been implemented as a graphical user interface (GUI) for ease of operation. Operating Systems themselves have no user interfaces, and the user of an OS is an application, not a person. The operating system forms a platform for other system software and for application software. Microsoft Windows, Linux, and Mac OS are some of the most popular OS's.

This is the interface between the user of a computer system and the hardware. A basic functional definition is that it is a program that makes the computing power available to users by controlling the hardware. A much better definition would be "a set of processes permanently or transitively resident within the computer that makes the resources of the computer available to the user in a consistent, reliable and friendly way. " The friendly bit though, would not quite apply to UNIX.It is therefore, a resource optimiser and operational manager. ...